1. Field of the Invention
The present invention relates, in general, to granulocytic Ehrlichia (GE) proteins. In particular, the present invention relates to nucleic acid molecules coding for GE S2, S7, S22, S23, C6.1, C6.2, S11, E8, E46#1, and E46#2 proteins; purified GE S2, S7, S22, S23, C6.1, C6.2, S11, E8, E46#1, and E46#2 proteins and polypeptides; recombinant nucleic acid molecules; cells containing the recombinant nucleic acid molecules; antibodies having binding affinity specifically to GE S2, S7, S22, S23, C6.1, C6.2, S11, E8, E46#1, and E46#2 proteins and polypeptides; hybridomas containing the antibodies; nucleic acid probes for the detection of nucleic acids encoding GE S2, S7, S22, S23, C6.1, C6.2, S11, E8, E46#1, and E46#2 proteins; a method of detecting nucleic acids encoding GE S2, S7, S22, S23, C6.1, C6.2, S11, E8, E46#1, and E46#2 proteins or polypeptides in a sample; kits containing nucleic acid probes or antibodies; bioassays using the nucleic acid sequence, protein or antibodies of this invention to diagnose, assess, or prognose a mammal afflicted with ehrlichiosis; therapeutic uses, specifically vaccines comprising GE S2, S7, S22, S23, C6.1, C6.2, S11, E8, E46#1, and E46#2 proteins or polypeptides; and methods of preventing ehrlichiosis in an animal.
2. Related Art
Granulocytic ehrlichiosis is an acute, potentially fatal tick-borne infection. The causative agent, granulocytic Ehrlichia (GE), has been identified by the polymerase chain reaction (PCR) using universal primers for eubacterial 16S ribosomal RNA (rRNA) to amplify the DNA of infected patients' blood (Chen et al., J. Clin. Micro. 32:589-595 (1994)). Comparison of the 16S rRNA gene sequence of GE to other known 16S rDNA sequences revealed a nearly identical match to the 16S genes of Ehrlichia phagocytophila and Ehrlichia equi (Chen et al., 1994). Two other groups of Ehrlichia species have also been categorized according to their 16S rRNA gene sequences, the Ehrlichia canis and Ehrlichia sennetsu groups. The E. canis and E. sennetsu species predominantly infect mononuclear phagocytes (Dumler et al., N. Eng. J. Med. 325:1109-1110 (1991)), whereas members of the E. phagocytophila group including GE are tropic for granulocytes (Ristic et al., in Bergey's Manual of Systemic Bacteriology, Kreig et al., eds., (1984), pp. 704-709). The near identity of the 16S rRNA gene sequences and the sharing of significant antigenicity by IFA and immunoblot (Dumler et al., J. Clin. Micro. 33:1098-1103 (1995)) indicate that E. phagocytophila, E. equi, and GE are closely related.
Full classification of the E. phagocytophila species including antigenic relationships among the individual isolates has been impeded by the inability to cultivate these organisms in cell culture. It has been shown that GE can be successfully cultivated in HL60 cells, a human promyelocytic leukemia cell line (Coughlin et al., PCT Application No. PCT/US96/10117; Goodman et al., N. Eng. J. Med. 334:209-215 (1996)). Walker et al., PCT Application No. PCT/US97/09147 teaches an isolated gene encoding a 120 kDa immunodominant antigen of E. chaffeensis that stimulates production of specific antibodies in infected humans.
The present invention describes GE specific genes encoding ten proteins (S2, S7, S22, S23, C6.1, C6.2, S11, E8, E46#1, and E46#2) which can be used as diagnostic reagents and vaccines.